[ruby/irb] Use class methods of `File` over `Kernel.open`

https://github.com/ruby/irb/commit/e0ec5e1bd8

lib/irb/ext/save-history.rb

@@ -70,7 +70,7 @@ module IRB
       end
       history_file = IRB.rc_file("_history") unless history_file
       if File.exist?(history_file)
-        open(history_file, "r:#{IRB.conf[:LC_MESSAGES].encoding}") do |f|
+        File.open(history_file, "r:#{IRB.conf[:LC_MESSAGES].encoding}") do |f|
           f.each { |l|
             l = l.chomp
             if self.class == RelineInputMethod and history.last&.end_with?("\\")